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Cytoskeleton Changes in Mesenchymal Stem Cells Differentiate to Osteoblasts and Chondrocytes and Effect of Electric Stimulation During Three-dimensional Scaffold Culture.  C. Umeda¹, Y. Kawahara^1,3, R. Yoshimoto¹, T Kajiume², A. Sasaki¹, S.L. Wu, ¹ K. Naminohira¹ and L. Yuge^1,3. ¹Graduate School of Health Sciences, ²Graduate School of Biomedical Sciences, ³Space Bio-Laboratories Y.K., Hiroshima University, Japan.

   The Rho GTPase has been influence cell morphogenesis through remodeling of the actin cytoskeleton and has been implicated lineage commitment of hMSCs. Here, we showed actin stress filaments formation and Rho activity when MSCs differentiate into osteoblasts and chondrocytes. Human MSCs were cultured in osteogenic induction medium and chondrogenic induction medium. Histological examination by light microscope showed that elongated shape cell has long process in osteoblast, while round or polygonal morphology in chondrocyte. The organization of actin filaments and stress fiber were examines by immunostaining with Rhodamine conjugated phalloidin and anti vinculin antibody for focal contact form. A remarkable difference in cytoskeleton organization was observed between in human MSCs during osteogenic and chondrogenic. In osteoblast, random and thin actin filaments and a few focal contact. While, in chondrocyte, parallel and thick actin filament as stress fiber was observed and a large number of focal contact. The activity of Rho analyzed by pull-down assay was no distinct difference in osteoblast and chondrocyte. Balance of mDia and ROCK activities decides to induce stress fiber and focal contact formation. And we examined that three-dimensional scaffolds seeds with cultured MSCs were applied to electrical stimulation.